Devices are conventionally employed on power boats for selectively adjusting or trimming boat attitude under varying load and sea conditions as the boat is powered through the water. For example, U.S. Pat. No. 3,695,204 discloses a trim control system in which a pair of trim tabs are pivotally mounted at laterally spaced positions on the boat stern. A pair of hydraulic fluid actuators extend between the boat hull and the respective trim tabs, and are connected to a valve and pump system coupled to an operator control for selectively adjusting positions of the respective trim tabs independently of each other. Other attitude trim control devices are known in the art.
Although the trim control system disclosed in the above-noted patent has enjoyed substantial commercial acceptance and success, improvements remain desirable. For example, when the engine is shut down, the trim tabs remain in the positions last selected by the operator. When the engine is restarted for powering the boat, the operator may not be aware of the positions of the trim tabs. Further, if the trim tabs and actuators remain extended, hydraulic pressure is maintained in the trim tab actuators during non-use, and unnecessary marine growth may occur on the actuating cylinders. There is also a risk of damage to the trim tabs from fork lifts, trailers and dry storage racks.
A general object of the present invention, therefore, is to provide a trim tab control system that includes facility for automatically returning the trim tabs to the fully retracted positions when engine operation is terminated. Another and more specific object of the present invention is to provide a trim tab control system of the described character that can be installed in the aftermarket on existing power boats by relatively unskilled personnel.